Several endocrine tumor markers are routinely used in the diagnosis and management of various cancers. The current assays, however, typically take several hours to perform, which precludes their use in the intraoperative management of patients. Most endocrine tumor markers have a half-life in the circulation of less than 5 minutes, thus making it feasible, if a rapid assay were available, for monitoring the concentration of the hormones during surgery or localization procedures. The primary indication for such assays would be to assess the extent of residual tumor after surgery and to localize tumors by selective venous or arterial sampling. In the past year, we have completed the development of a new intact PTH assay that does not cross react with the 7-84 fragment of PTH. We have compared the old and new rapid PTH assay and have found that there is faster decay of PTH with the new assay following parathyroidectomy. We have also completed an analysis of the possible diagnostic utilty of a rapid ACTH assay on jugular venous samples. The results showed that such an assay would be useful for preventing the need for petrosal venous sampling in about 50% of the cases for Cushing's disease. In the upcoming year, we plan to further develop a rapid gastrin assay for localizing gastrinomas.